今天，昨天，这个星期，上个星期，这个月，上个月... 变量

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Adapted from the Date and Time Programming Guide:

// Right now, you can remove the seconds into the day if you want
NSDate *today = [NSDate date];


// All intervals taken from Google
NSDate *yesterday = [today dateByAddingTimeInterval: -86400.0];
NSDate *thisWeek  = [today dateByAddingTimeInterval: -604800.0];
NSDate *lastWeek  = [today dateByAddingTimeInterval: -1209600.0];


// To get the correct number of seconds in each month use NSCalendar
NSDate *thisMonth = [today dateByAddingTimeInterval: -2629743.83];
NSDate *lastMonth = [today dateByAddingTimeInterval: -5259487.66];

If you want the correct exact number of days depending on the month, you should use an NSCalendar.

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最佳答案

Might be a better way to write this but here what i came up on Ben's NSCalendar suggestion and working from there to NSDateComponents

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *components = [cal components:( NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond ) fromDate:[[NSDate alloc] init]];


[components setHour:-[components hour]];
[components setMinute:-[components minute]];
[components setSecond:-[components second]];
NSDate *today = [cal dateByAddingComponents:components toDate:[[NSDate alloc] init] options:0]; //This variable should now be pointing at a date object that is the start of today (midnight);


[components setHour:-24];
[components setMinute:0];
[components setSecond:0];
NSDate *yesterday = [cal dateByAddingComponents:components toDate: today options:0];


components = [cal components:NSWeekdayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:[[NSDate alloc] init]];


[components setDay:([components day] - ([components weekday] - 1))];
NSDate *thisWeek  = [cal dateFromComponents:components];


[components setDay:([components day] - 7)];
NSDate *lastWeek  = [cal dateFromComponents:components];


[components setDay:([components day] - ([components day] -1))];
NSDate *thisMonth = [cal dateFromComponents:components];


[components setMonth:([components month] - 1)];
NSDate *lastMonth = [cal dateFromComponents:components];


NSLog(@"today=%@",today);
NSLog(@"yesterday=%@",yesterday);
NSLog(@"thisWeek=%@",thisWeek);
NSLog(@"lastWeek=%@",lastWeek);
NSLog(@"thisMonth=%@",thisMonth);
NSLog(@"lastMonth=%@",lastMonth);

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I really like the THCalendarInfo object contained in this project:

http://github.com/jaredholdcroft/kcalendar

I can't quite find the original. Using this object you can move to a previous day, the start of a week, the start of a month, get the day of a week, the day of a month... etc. etc.

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NSDateComponents is nice to get today:

NSCalendar *cal = [NSCalendar currentCalendar];


NSDate *date = [NSDate date];
NSDateComponents *comps = [cal components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit)
fromDate:date];
NSDate *today = [cal dateFromComponents:comps];

This creates a NSDate with only year, month and date:

(gdb) po today
2010-06-22 00:00:00 +0200

To get yesterday, etc. you can calculate it using NSDateComponents:

NSDateComponents *components = [[NSDateComponents alloc] init];
[components setDay:-1];
NSDate *yesterday = [cal dateByAddingComponents:components toDate:today options:0];

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NSDate *today = [[NSDate alloc] initWithTimeIntervalSinceNow:0];

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+ (NSDate*)dateFor:(enum DateType)dateType {


NSCalendar *calendar = [NSCalendar currentCalendar];


NSDateComponents *comps =
[calendar components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
fromDate:[NSDate date]];


if(dateType == DateYesterday) {


comps.day--;
}
else if(dateType == DateThisWeek) {


comps.weekday = 1;
}
else if(dateType == DateLastWeek) {


comps.weekday = 1;
comps.week--;
}
else if(dateType == DateThisMonth) {


comps.day = 1;
}
else if(dateType == DateLastMonth) {


comps.day = 1;
comps.month--;
}
else if(dateType != DateToday)
return nil;


return [calendar dateFromComponents:comps];
}

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NSDate *today = [NSDate date]; // Today's date
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *weekdayComponents =[gregorian componentsNSDayCalendarUnit | NSWeekdayCalendarUnit) fromDate:today];
NSInteger day = [weekdayComponents day];

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The other answers just didn't work for me (maybe because of my time zone). This is how I do it:

- (BOOL)isOnThisWeek:(NSDate *)dateToCompare
{
NSCalendar * calendar = [NSCalendar currentCalendar];
NSDate     * today    = [NSDate date];


int todaysWeek        = [[calendar components: NSWeekCalendarUnit fromDate:today] week];
int dateToCompareWeek = [[calendar components: NSWeekCalendarUnit fromDate:dateToCompare] week];


int todaysYear         = [[calendar components:NSYearCalendarUnit fromDate:today] year];
int dateToCompareYear  = [[calendar components:NSYearCalendarUnit fromDate:dateToCompare] year];


if (todaysWeek == dateToCompareWeek && todaysYear == dateToCompareYear) {
return YES;
}


return NO;
}

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Swift 4.2

let today = Date()
let yesterday = today.addingTimeInterval(-86400.0)
let thisWeek = today.addingTimeInterval(-604800.0)
let lastWeek = today.addingTimeInterval(-1209600.0)


let thisMonth = today.addingTimeInterval(-2629743.83)
let lastMonth = today.addingTimeInterval(-5259487.66)


// components of the date
let calendar = Calendar(identifier: Calendar.Identifier.gregorian)
let components = calendar.dateComponents([.year, .month, .day], from: today)
let (year, month, day) = (components.year, components.month, components.day)

Please note that date components are optional.

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This is for check the date is this month or not

func isOnThisMonth(dateToCompare: NSDate) -> Bool {
let calendar: NSCalendar = NSCalendar.currentCalendar()
let today: NSDate = NSDate()
let todaysWeek: Int = calendar.components(NSCalendarUnit.Month, fromDate: today).month
let dateToCompareWeek: Int = calendar.components(.Month, fromDate: dateToCompare).month
let todaysYear: Int = calendar.components(NSCalendarUnit.Year, fromDate: today).year
let dateToCompareYear: Int = calendar.components(NSCalendarUnit.Year, fromDate: dateToCompare).year
if todaysWeek == dateToCompareWeek && todaysYear == dateToCompareYear {
return true
}
return false
}

And second one only change type of calendarUnit for weak like this

func isOnThisWeek(dateToCompare: NSDate) -> Bool {
let calendar: NSCalendar = NSCalendar.currentCalendar()
let today: NSDate = NSDate()
let todaysWeek: Int = calendar.components(NSCalendarUnit.Weekday, fromDate: today).weekday
let dateToCompareWeek: Int = calendar.components(.Weekday, fromDate: dateToCompare).weekday
let todaysYear: Int = calendar.components(NSCalendarUnit.Year, fromDate: today).year
let dateToCompareYear: Int = calendar.components(NSCalendarUnit.Year, fromDate: dateToCompare).year
if todaysWeek == dateToCompareWeek && todaysYear == dateToCompareYear {
return true
}
return false
}

I hope this is helpful to someone Thanks.

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I answered a similar question already and here's why my answer is better:

Swift 3!
Utilizes DateFormatter's "Yesterday" and "Today". This is already translated by Apple, which saves you work!
Uses DateComponentsFormatter's already translated "1 week" string. (Again less work for you, courtesy of Apple.) All you have to do is translate the "%@ ago" string. 🙂
The other answers incorrectly calculate the time when the day switches from "today" to "yesterday" to etc. Fixed constants are a big NO-NO because reasons. Also, the other answers use the current date/time when they should use the end of the current day's date/time.
Uses autoupdatingCurrent for Calendar & Locale which ensures your app is immediately up to date with the user's calendar and language preferences in Settings.app

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If you're using iOS 10+ or MacOS 10.12+, you can use these two Calendar methods to do this properly.

func date(byAdding component: Calendar.Component, value: Int, to date: Date, wrappingComponents: Bool = default) -> Date? (docs)
func dateInterval(of component: Calendar.Component, for date: Date) -> DateInterval? (docs)

Here's an example of how to use these methods in Swift 3, along with the playgrounds output in my time zone.

let calendar = Calendar.current
let now = Date()
// => "Apr 28, 2017, 3:33 PM"


let yesterday = calendar.date(byAdding: .day, value: -1, to: now)
// => "Apr 29, 2017, 3:33 PM"
let yesterdayStartOfDay = calendar.startOfDay(for: yesterday!)
// => ""Apr 29, 2017, 12:00 AM"


let thisWeekInterval = calendar.dateInterval(of: .weekOfYear, for: now)
// => 2017-04-23 04:00:00 +0000 to 2017-04-30 04:00:00 +0000


let thisMonthInterval = calendar.dateInterval(of: .month, for: now)
// => 2017-04-01 04:00:00 +0000 to 2017-05-01 04:00:00 +0000


let aDateInLastWeek = calendar.date(byAdding: .weekOfYear, value: -1, to: now)
let lastWeekInterval = calendar.dateInterval(of: .weekOfYear, for: aDateInLastWeek!)
// => 2017-04-16 04:00:00 +0000 to 2017-04-23 04:00:00 +0000


let aDateInLastMonth = calendar.date(byAdding: .month, value: -1, to: now)
let lastMonthInterval = calendar.dateInterval(of: .weekOfYear, for: aDateInLastMonth!)
// => 2017-03-26 04:00:00 +0000 to 2017-04-02 04:00:00 +0000

Bonus: You can use the DateIntervals to test whether a date falls in that range. Continuing from above:

thisWeekInterval!.contains(now)
// => true
lastMonthInterval!.contains(now)
// => false